基于ERA 40资料的边界层厚度气候特征分析

An analysis of planetary boundary layer depth climatic features based on ERA 40 dataset

为了解边界层厚度的大尺度分布及其气候循环特征,基于逐日ERA 40再分析边界层厚度资料,采用统计学方法计算边界层厚度分4个时次的季节循环、年较差等气候特征场,对全球边界层厚度分布及其季节演变特征进行了研究。结果表明:全球较厚的边界层分布与大地形、沙漠等下垫面的分布有直接联系;陆地强边界层分布存在"08时"现象,即陆地较厚边界层中心分布在当地时间08时经线附近;在大洋上南北纬30°～40°两条纬度带内边界层厚度的月尺度内变率较大,与大气强斜压性的天气系统活跃区一致;月平均日较差的年循环特征存在着季节性南北进退的现象。研究结果对于全面认识和科学利用ERA 40逐日边界层再分析资料有一定帮助。

In order to acquire large scale distribution and climatic cycle features of planetary boundary layer（PBL） depth,based on daily ERA 40 PBL depth dataset,the global PBL depth distribution and seasonal evolution are investigated by means of climatic feature fields such as seasonal cycle,annual difference,which are divided into 4 time levels and computed through statistical method.Result shows that there is a direct relation between thicker PBL depth and planetary surface property,e.g.plateaus or deserts.Continental thicker PBL depth distribute is characterzed by an 8 o＇clock pattern,that is,over the continents the thicker PBL depth center lies around the longitude of local time 8 o＇clock.Over oceans there are two large intra-monthly variability bands between 30 to 40 latitudes in north and south hemisphere respectively,both bands are consistent with the strong atmospheric baroclinic and active weather system regions.Monthly mean daily difference of PBL depth shifts northward and southward with seasonal circulation.The result is helpful to overall understanding and scientifical application of ERA 40 PBL depth dataset.